Electrochemical measurement means a method of measuring properties of chemical substances electrically. As an example of a measuring instrument to perform the electrochemical measurement, an electrochemical measurement flow cell disclosed in PTL 1 is known. The electrochemical measurement flow cell has a structure in which a flow channel is provided in a body having chemical resistance such as PEEK and electrodes are arranged to contact the flow channel and is mainly used as a detector of liquid chromatography or flow injection analysis.
In the electrochemical measurement flow cell, a solution containing a measurement target substance is introduced into the flow channel and measurement is performed. After the measurement, appropriate cleaning is performed and the electrochemical measurement flow cell is repetitively used. The electrodes used for the electrochemical measurement generally include three kinds of electrodes to be a working electrode, a counter electrode, and a reference electrode. For the working electrode and the counter electrode among these electrodes, stable metals such as platinum are used to prevent the electrodes from affecting a reaction of the measurement target. The reference electrode is an electrode having a special function of maintaining a potential constantly and a silver/silver chloride electrode is used as the reference electrode.
The electrochemical measurement flow cell is generally used for the repetitive measurement after the appropriate cleaning. Because the electrochemical measurement flow cell has a relatively complicated structure with the electrodes and the flow channel, it is not preferable to use the electrochemical measurement flow cell as a disposable product, from the viewpoint of a cost and maintenance. As the electrochemical measurement flow cell is repetitively used, a measurement value may be changed due to a change of an electrode property, a change of a flow channel structure, and contamination of an inner portion of the flow cell. In addition, the measurement value may not be correctly obtained due to unexpected events such as adhesion of a chemical substance to an electrode surface, mixture of air bubbles in the flow channel, and damages of the electrodes. As described above, in the abnormal case, it may be predicted that a current flowing between the electrodes changes as compared with the normal case, the abnormality may be detected by monitoring a current value, and the possibility of incorrect measurement may be communicated.